Empty schema error when I try to post a new Avro schema to Kafka schema-registry

Question

I am using Confluent Platform for a MongoDB Sink Connector and I need to define an Avro schema in the Schema Registry so that data would be written in a structured manner to MongoDB Collection.

I have saved the following schema in a .avsc file:

{
    "type": "record",
    "name": "Transaction",
    "namespace": "com.prxm",
    "fields": [
        {"name": "Timestamp", "type": "Date"},
        {"name": "Price", "type": "double"},
        {"name": "Qty", "type": "int"},
        {"name": "Name", "type": "string"}
    ] 
}

I tried to post this schema to Kafka Schema Registry using the following cURL command:

curl -X POST -H "Content-Type: application/vnd.schemaregistry.v1+json" --data @transaction-schema.json http://localhost:8081/subjects/transaction-value/versions

And got the following error: {"error_code":42201,"message":"Empty schema"}. I Googled it and searched across Stackoverflow but didn't find a proper solution.

Confluent version: 7.3.2 Connect is UP and so is Schema Registry Running on Ubuntu 22 VM.

Any help would be appreciated.

Answer 1

My bad, the correct way to post this schema to Confluent Schema Registry is this:

curl -X POST -H "Content-Type: application/vnd.schemaregistry.v1+json" --data '{"schema": "{\"type\":\"record\",\"name\":\"Transaction\",\"namespace\":\"com.prxm\",\"fields\":[{\"name\":\"Timestamp\",\"type\":\"string\", \"logicalType\": \"Date\"},{\"name\":\"Price\",\"type\":\"double\"},{\"name\":\"Qty\", \"type\": \"int\"},{\"name\": \"Name\", \"type\": \"string\"}]}"}' http://localhost:8081/subjects/transaction-value/versions

Note that --data argument should include the whole schema in JSON format and not a reference to a file.

Another important thing I noticed is that the Kafka Topic (named "transaction" in this example) should be created via the Confluent Platform, don't rely on older Topics which were created by Apache Kafka CLI as an according Subject wouldn't be created in the Schema Registry.